Telephone system.



L. C. BYGRAVE.

TELEPHONE SYSTEM. APPLICATION FILED JAN-19,1916.

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TELEPHONE SYSTEM. APPLICATION FILED JAN. 19, I916.

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TELEPHONE SYSTEM. -APPLICAT|0N FILED JAN. 19, 1916.

Patented July 24, 1917.

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L. C. BYGRAVE.

TELEPHONE SYSTEM. APPLICATION FILED JAN. 19, 1916.

Patented July 24, 1917.

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LEONARD CHARLES BYGRAVE, OF LONDON, ENGLAND, ASSIGNOR TO THE RELAY AUTOMATIC TELEPHONE COMPANY, LIMITED, OF LONDON, ENGLAND.

TELEPHONE SYSTEM.

Specification of Letters Patent.

Patented July 24, 1917.

Application filed January 19, 1916. Serial No. 72,967.

This invention relates to automatic and semi-automatic telephone systems which utilize relays instead of step by step electromechanical devices.

The principal object of the invention is to reduce the number of relays required on such systems already known, to simplify the connections, to give greater flexibility and to" simplify wiring and maintenance.

The invention refers to switching units made up of relays which may be associated one with each subscribers line or junction to give access to a plurality of other lines, or may be associated with a plurality of subscribers lines, as for example, when used as a calling line finder.

The switching unit may be associated with either an assignor which automatically and instantly causes the switch to connect a calling line to an idle junction line or with a responder which responding to impulses completes or assists to complete circuits to a particular line or group of lines.

The invention is illustrated in the accompanying drawings in which Figure 1 shows switching units employed as calling line finders while Fig. 2 shows switching units employed as connectors. Fig. 3 shows in single line diagram a two-digit switching unit. Fig. 4 shows the circuit of a calling line finder switching unit in which the next idle junction is pre-selected.

Fi 5 shows the circuit of a direct calling two-digit switching unit combined with a responder.

In Fig. 1 the switching units S, S", S" consisting of the two parts T and U 've any of the lines L, which may be callmg, access to one of the associated junctions J J, J. As a junction J, for instance, is taken into use it is of course made busy so that the switching unit S associated with the next idle junction J is used. Such a switching unit is a calling line finder preselector.

In Fig. 2 the switching units S, S", S are shown associated one with each subscribers line L and act as direct calling pro-selectors to find an idle junction J. They may also be employed to connect L to a particular junction J determined by an associated impulse responder.

In Fig. 3 a switch is shown arranged to give a line J access to one of a plurality of lines L or to give one of a plurality of lines L access to a line J according to whether the switch is used as a pro-selector or as a calling line finder.

The switch is shown as consisting of fourteen relays a to a, ten of which a to j respond and switch according to units impulses, while the remaining four relays k to n respond and switch according to the tens impulses received; thus, if the relay a is operated, all those lines, the unit digit of which is 1, are connected to the ten wires 19 and if relay 7c is also operated the top wire 10 and therefore numberll will be connected to the junction J by circuit 11, all the other wires 7) being isolated at one or other of the contacts of the relays k to a. If relays a and Z are operated, line 21 is connected. If 6, m and n are operated, O is connected and so on, the connection of othernumbers being easily traceable.

In Fig. l circuits are shown for two Q-digit switching units acting as calling line finders, as in Fig. 1. Each unit is shown arranged to give forty lines access to one junction. Only four levels are shown corresponding to levels 71 to O of Fig. 8. That figure shows the usual ten levels for a 100 line switch. Each level actually consists of three wires, one from each of the groups A, B, C, making up a level. A and B are the talking circuits and C the test wires. Two subscribers are represented at X whose numbenlet us assume is and Y whose number let us assume is 84, and two junctions at J J When a subscriber, X for instance, calls by takinghis receiver off the switch hook (not shown) he completes circuit 2 through line relay X and a common relay A. X and A operate, the former connecting negative potential to certain of the code wires C IV, and the latter connecting the test wires T W of all the junctions to the assignor A Assuming that all the junctions J *,-J are idle, none of the assignor relays, except B which is a battery switching relay, will be energized. B is operated in circuit 3 and completes circuit 4 through relay C which operates and switches all the coding wires C W to switching unit S In order to connect line X, 0 to a junction, it is necessary to operate relays a, m and n of the switching unit, therefore X is arranged to connect the negative side of battery to the three coding wires associated with those three relays over circuits 5, 6 and 7. a, m and n on operating connect X to junction J a over circuit 8 and through relay D, which may be directly or indirectly associated with the junction loop at the same .or the next stage. D operates andcompletes circuit .9 through out off relay E and through a, m and n in parallel. a, m and n are therefore maintained as long as the subscriber has his receiver off the switch hook. The operation of E cuts out relay X and A, the former cutting circuits 5, 6 and 7., the latter releasing ,assignor A If while the first junction is busy another subscriber, Y, No. 84:, for instance, originates a call, circuit 10 will be completed through relays Y and A, Y connecting code 11, 12, 13 to code wires G T, and A connecting test wires T to assignor A Junction J beingbusy, circuit 11% is completed through assignor relay F which operating completes circ it 1 through rel y G to connect t e code wires to the relays of the second switching unit S Code 311, 12,, 13 will therefore cause rela s il 2 and to o crate connecting line Y .over circuit 16 to junction J". Relay will therefore operate to complete circuit 17 operating out ofl relay Y and loc ing y y and The switch would then be associated with a junction as shown in Fig. 2. For the first series of impulses one or more of the relays 7a to n will be energized, and in answer to a second series one of the relays a to y will be energized. Thus line J, Fig. 3, would be connected to a particular .one of the lines L. to a may, for instance, control connection to the tens and a to 7' connection to the units.

In a further modification of the invention the unit may be arranged so that the responder itself forms part of the unit.

' Fig. 5 shows circuits of a switching unit in which an impulse responder first initially energizes switching relays in response to one set of digit impulses and then, after completing preparatory circuits, in response to another set of digit impulses the resultant particular relays associated with the digit remain energized to switch a connection through and to maintain the circuit during connection.

The responder consists, as described for instance in British specification No. 1470 of L915, of relays H, I, J, K, L, M, N, O. After responding to impulses of the first of'two digits the responder momentarily completes a circuit to energize one of a group of relays associated with the tens digit which then locks itself in local circuit. When the responder energizes by the second digit pulses, certain relays of the responder, corresponding to the digit sent, energize and lock themselves in local circuits and remain so locked during the period .of conversation, after having joined the calling line through to one circuit of ten in the tens group previously called.

Circuit 1 corresponds to a circuit from a subscribers instrument but may be completed by a repeater or other device, at a previous stage. In this circuit l is energized, when a call is made, to complete cirwit 2 in hi h 2E i e ergized- 2 is slo to relea e so that h n 1 n rgi e a energizes according to the impulses received, 2 will not have time to decnergize and certain circuits will therefore be kept energized during the impulses. 2 completes circuit 3 in which 3 i energized- ,It is to be n t that circuit 3 is completed over responder relays H, I, J K so that when one .of these relays is energized for a period long enough 3 will deenergize. completes circuit & to energize L, 2 completes a holding circuit 5 over the previous switching stage. A circuit.

6 is completed in which G is energized but serves no .usefulpurpose at the moment and has nothing to do with this invention. Digit switching relay 7 is energized in circuit 7. It will be assumed that No. ll is to be called. When circuit 1 is opened on the break of the first impulse, 1 is deenergized and circuit 8 is completed to energize H as is a re.- tain-ing circuit 9 for L. d

hen 1 is energized at the completionflof the first impulse a retaining circuit for H is completed over circuits 1,0 and 4. Circuit 11, completed attwo points, namely, by 7 and 2 en rgiz s L e ne g' z s as circuit 8 is broken at 1 H and M only remain energized at this stage. As, however, H has opened circuit 3 relay 3? deenergizes, which cuts earth ofi circuit 4 so that H deenergizes. M is maintained energized by earth at 7 3 deenergizing completes circuit 12 to enerj gize No. 1 switching relay 12 of the tens digit switch which is then retained in a local circuit 13 to earth at 2 This happens in the time interval between the opening of the circuit 7 at 3 and the dei llergization of 7 which is slow to release. 7 opens circuit 11 so that M deenergizes. All the relays of the impulse responder are again at normal.

The second digit 1 is now sent by the cal er en ir -y i t en rgizcd as befo ancl- 2 remain en rgiz d, 3E is also. energized as circuit 3 is completed over H. Circuit 4 is therefore completed and L is ene giz d i n ergize sthe Cir cuit is now open at 112 H is energized over 8 a d M is nergized over to earth at lVhen 1 is again energized H is retained over 4:. has opened circuit 3 so that deenergizes Circuit 14 at relay 3- must be madezbe ore & and 1 are broken, ethat the earth cut of? may be replaced by earth over 21 Without break. If necessary another slow release relay controlled by 3 may be introduced which will keep earth on 4 and 11 after 3 has joined up circuit 14. 14 energizes in series with out 01f relay C O R if the line called is idle. H and M are kept energized over circuit 21. 14 is retained energized over 15 and C O R is retainedenergized over 21 and 14 The calling line is now extended to the called line by loop 16 and 17. Circuit 14 being the third conductor retaining circuit. Circuit 18 causes 18 to energize to connect the calling line to the ringing generator with relay 19 in series. 19 does not respond with the called station condenser in series with the bell, but when the receiver is lifted to answer it energizes to complete circuit for 20 which opens circuit 18 to join the lines through for talking. Relay 16 is then energized.-

The combination described places the power of release or disconnection in the hands of the calling party by replacing the receiver and opening the circuit of 1 when all apparatus is restored to normal. Should he fail to release the connection the called party can denergize 16 when circuit 22 will be completed to glow lamp 22 and/or give an audible signa Should the called party be engaged relay 14 will not energize as the cutoff relay will be earth connected and insufiicient current will be obtainable. Circuit 21 will not be completed at 14 and 3 will deenergize and release H so that circuit 6 will be completed to energize 6 and local retaining circuit 6 made, and circuit 24 will be completed to connect the busy tone to the loop circuit.

Under certain conditions, particularly for small installations, the tens and units relays may be energized in reversed order, for example, what have been called the tens relays may become the units and the responder be afterward tied up to the units.

What I claim is 1. In a telephone system, the combination with a plurality of lines of a plurality of wires, a plurality of relays each adapted to connect a number of said lines to a corresponding number of said wires, each to each, and a plurality of combining relays less in number than said Wires and adapted to complete a connection through any one of said wires.

2. In a telephone system, the combination with a plurality of lines of a plurality of wires, a group of relays each of which is adapted to connect each of the wires to a line, a junction and a second group of relays capable of being actuated alone or in combination and adapted to connect any one of the wires to the junction.

LEONARD CHARLES BYGRAVE.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. 0. 

